Starting today, you can book SNCF tickets for January 9 to March 29.

I will present to you a sample route, but I might come back with other examples since I'm interested in a few more destinations.

Paris (Gare de Lyon) to Cannes

The journey begins at 08:22 and after 5h06m arrives in Cannes at 13:28.

The train has two more stops at no extra cost: Antibes (at 13:41) and Nice (at 14:06).

€19 for an adult, €8 for a child.

For us, two adults and a child, it costs €46, but I prefer to pay €3/adult extra to reserve the seats with a table on the upper deck. Kids' reservation is free, and on the lower deck is €7 for an adult.