Chatime has a pretty awful app you can exploit. When you make a new account, you will receive a 50% off first drink voucher, which can be claimed anytime, as long as you apply it at the checkout. It isn't in big bold letters, so try to make sure you have applied it before you pay. Simply order a drink worth $7.60 or more to get the max $3.80 discount. Bear in mind that it is capped at $3.80, so if you get an $8 drink the final payment is $4.20.
Now this only works for first time customers. But since you can delete your account and make a new one instantly, all you have to do is make an account, use the voucher up, delete the account and make a fresh one. You should have a new voucher ready to go. Chatime does not have an account creation cooldown timer or locks details like your phone number to one account - you can repeat this as much as you like. Hope it doesn't get patched soon.
not sure if this is a hack, but i'll agree their app is just as bad as their marketing