You'll have a hard time finding most Estonian brands outside of Estonia.
Põltsamaa Kange Sinep is a good strong mustard. Goes well with fatty meat. If you treat it like the stuff people put on hot dogs, you'll also be rid of your nasal congestion.
Mayer makes affordable and often hypoallergenic household cleaning stuff. Soap, dish soap, laundry detergent. Usually very mild smelling stuff too.
Wise lets you receive money in a bunch of different currencies, keep balance in said currencies or convert them, has cheap conversions in general. Not a product, more of a service, but thought I'd throw it out there.
Värska makes some pretty good mineral water. I mean Värska Originaal in particular.
Traditional old Limonaad if you're into soft drinks. Yes it's just labeled "lemonade" and everyone knows what you mean. It's also technically not a lemonade.
If your soft drink of choice is craft beer, though, Pühaste, Põhjala and Anderson's make some good ones.