Here is a guide and Cheat Sheet on how to complete all of the challenges for the 14 Days of Summer Fortnite Event before it ends.
There was a new challenge released for every day of the 14 Days of Summer Event in Fortnite Battle Royale and completing each of these challenges gives players a different reward and completing all of the challenges will earn you an extra reward.
Here are all of the challenge guides by day and the rewards for each day if you only want to earn select rewards. The Cheat Sheet is at the bottom of this article if you would prefer that.
Make sure you complete the challenge before the event ends as these rewards are exclusive and cannot be awarded in any other way.
14 Days of Summer Day 1 Challenge – Dance at different beach parties
The very first challenge for the event was the “Dance at different beach parties” challenge and in order to complete this challenge, players are required to dance at six different locations. We have a map below for all the locations:

The reward for completing this challenge is the deep end emote:
Dance at different beach parties to get the Deep End Emote! pic.twitter.com/kf055KD41J
— Fortnite (@FortniteGame) June 25, 2019
14 Days of Summer Day 2 Challenge – Bounce a giant beach ball in different matches
The second challenge to be released for the 14 Days of Summer Event is to “Bounce a giant beach ball in different matches“. To complete this challenge, players are required to bounce a giant beach ball in five different matches. We have marked the locations of the giant beach balls on the map below. There are only three beach balls but as you need to bounce the ball in different matches, you can keep landing at the same ball in different matches.

The reward for completing this challenge is the Soak it Up Loading Screen:

14 Days of Summer Day 3 Challenge – Eliminations with the daily unvaulted weapon or a Drumgun
The third challenge to be released is to get five “eliminations with the daily unvaulted weapon or a Drumgun”. As there are no more unvaulted weapons as the 14 days have finished, you will need to get these eliminations with the Drumgun and there is no guide necessary for this.

Here is the reward for completing this challenge:

14 Days of Summer Day 4 Challenge – Thank the Bus Driver and finish top 20 in different matches
The Day 4 Challenge is to “Thank the Bus Driver and finish top 20 in different matches”. You will need to do this in five different matches. To do this, simply thank the Bus Driver and land at a POI that is quite far from the bus route in order to avoid any players. You should be able to finish in the top 20 to complete this challenge.

The reward for completing this challenge is the Perfect Blend Emoticon:

14 Days of Summer Day 5 Challenge – Pop Party Balloon Decorations
The fifth challenge to complete is to “Pop party balloon decorations” and you will need to pop five in order to complete this challenge. We have created a map that shows the locations of the party balloons, as seen below:

The reward for completing day 5 is the Sunny Spray:

14 Days of Summer Day 6 Challenge – Search unicorn floaties at swimming holes
The Day 6 challenge is to “Search unicorn floaties at swimming holes” and you will need to search three in order to complete this challenge. The location of these floaties can be seen on the map below:

The reward you will receive for completing today’s challenge is the Neon Tropics Wrap:

14 Days of Summer Day 7 Challenge – Hit a player with a water balloon in different matches
The Day 7 challenge is to “Hit a player with a water balloon in different matches” and you will need to do this in three different matches to complete the challenge. The Water Balloon toy is awarded to players that have completed the Day 3 challenge and so you will have needed to complete this challenge before this one can be completed.

The reward for completing the seventh challenge is the Summertime Splashdown Loading Screen:

14 Days of Summer Day 8 Challenge – Bounce off a giant beach umbrella in different matches
The eight challenge is to “Bounce off a giant beach umbrella in different matches” and this will need to be done in three different matches. The location of the beach umbrellas is shown on the map below:

You will receive the duck banner for completing this challenge:

14 Days of Summer Day 9 Challenge – Score trick points with a Driftboard with the Neon Tropics applied to it
The ninth challenge is to “Score trick points with a Driftboard with the Neon Tropics applied to it” and you will need a total of 250,000 points in order to complete the challenge. The Neon Tropics wrap is unlocked by completing the Day 6 challenge.

Completing the Day 9 challenge will get you the Surfstick Spray:

14 Days of Summer Day 10 Challenge – Launch fireworks found along the river bank
The tenth challenge is to “Launch fireworks found along the river bank” and you will need to launch three in order to complete the challenge. The location of the fireworks have been shown on the map below:

The Day 10 reward is the Low ‘n Slow pickaxe, as seen below:

14 Days of Summer Day 11 Challenge – Get a score of 10 or more on a Carnival Clown Board
The Day 11 challenge is to “Get a score of 10 or more on a Carnival Clown Board” and you will only need to do this once in order to complete the challenge. The location of the boards can be seen below:

Completing this challenge will unlock the Beachballs contrail:

14 Days of Summer Day 12 Challenge – Visit a giant beach umbrella and a huge rubber ducky in a single match
The twelfth challenge is to “Visit a giant beach umbrella and a huge rubber ducky in a single match” and the location of the beach umbrellas can be seen below. The rubber ducky moves along the river so will not be in the exact same place in every match.

When you have completed this challenge, you will unlock the Quack Pack Back Bling:

14 Days of Summer Day 13 Challenge – Search the tiny rubber ducky at the spot hidden in the Summertime Splashdown loading screen
The Day 13 challenge is to “Search the tiny rubber ducky at the spot hidden in the Summertime Splashdown loading screen“. When this challenge was first released, once one player had searched the rubber duck, it would disappear and so only one could be searched in a match. Epic were aware that this made the challenge harder than intended and so anyone that had attempted to complete the challenge were given the reward. Here is the location of the duck:

Completing the penultimate challenge will award you with the Sparkles Music Pack:
Search for a tiny rubber ducky to earn the Sparkle Soundtrack Lobby Music! pic.twitter.com/o0AlcY4cHH
— Fortnite (@FortniteGame) July 7, 2019
14 Days of Summer Day 14 Challenge – Destroy grills with the Low ‘n Slow Harvesting Tool
The last challenge is to “Destroy grills with the Low ‘n Slow Harvesting Tool” and you will need to destroy seven grills in order to complete the challenge. You will have needed to complete the Day 10 challenge to unlock the Low ‘n Slow pickaxe. Here is a map with the grill locations:

Completing the last challenge will get you the Barbecue Banner, as seen below:

Once all challenges have been completed, you will also unlock the Smoothie Back Bling:

Here is a Cheat Sheet created by @thesquatingdog for the 14 Days of Summer Challenges:
