blandThe soup is very bland, it could use more herbs and spices.
flavourlessUKThese tomatoes from the grocer's are flavourless.
insipiddisapprovingHe was drinking an insipid light beer.
watered-downThe bar served bad food and watered-down cocktails.
wateryThe tea was too watery.
like dishwaterinformaldisapprovingThis tea tastes like dishwater!
weakThe punch was quite weak.