The Little White Train is famous around France. It's a good way to learn the history of Toulon and see the city.
Spend a few hours down by the beach. You can rent kayaks, paddle boards, sail boats, etc. There is also a trail along the rocks that takes you right under the venue - and has the best secret beaches!
Take the cable car to the top of the mountain. You can see the whole city from the top. There are hiking/walking trails and a restaurant up there.
Check out the largest market in Toulon. Open everyday until 12:30pm
There are a ton of vineyards around! The town one train stop over - Bandol - is also widely known for their wine!
Grab a towel + some goggle and head down to Mourillon beach.
Head down to the city center and shop around!