Hot ribena all the way
Smells lovely
and tastes lovely.
Also, if fruit juices don't hurt your mouth too much, smoothies are lovely and feel like a treat esp the 'innocent' ones, they are refreshing and good for you and full of vitamins and that might also help your mouth ulcers.
Hope you get better soon - heed the advice of the Cadbury's caramel bunny and take it easy