Best season: unless you avoid crowds, I enjoy it better in August, as they have their local celebrations.
Distance: 30 minutes by train from Barcelona, regular daily trains up to 10pm.
Sitges is a little beach town, although it is known as the Spanish gay city, it has a lot of charm and there are many wealthy properties there.
My favourite day in Sitges is 23rd August, where they show a firework display in the beach. I spend all day there, and I eat dinner before as it starts at 11pm. I tend to stay overnight, as the last train is at 10pm to Barcelona. You should book in advance as it is the highest season of all, plan B enquire for an Uber service beforehand, roads will be busy before and after the fireworks, so I recommend to take it easy.
With time: "Los Vikingos" have bikinis (see food section), and other nice breakfasts, specially a fruit salad which is obtained from a tiny shop right next to them. They also have "Horchata" but it is better in the afternoon.
Running late? Find "Carme Miranda" fruit shop or go straight for a quick lunch instead.
For easily burnt visitors: eat a paella by the beach seafront in "La Santa Maria" restaurant.
Do you want to tan? Pans & Company has patatas bravas and a baguette, my favourite is the "Extremeño" (thin pork loin and manchego cheese baguette) and tan away!
Providing you didn't have the paella in the morning, you can instead have proper dinner in "La Santa Maria".
Quick baguettes and fries, chistorra baguette is my favourite, a type of chorizo in "Sol y Sombra" which opens from late afternoon.
BARCELONA TO SITGES DAY TRIP
30 mins from a train station, either Plaça Catalunya (Metro L3 or L1) in the city centre or Sants Estació (Metro L3 or L5). If you are only one person, you can buy a day return ticket (not to be confused with Day card). You can buy a T-10 up to zone 4 for 34.45€, it gives you 10 trips via bus/underground/ferrocarril/tram from zones 1 to 4, so 3.45€ a trip. You can transfer two different methods of transport for free within 75 minutes from the 1st journey made. E.g. a bus/underground, bus/bus wouldn't apply. Selling points: any underground or train stations.