Is the word regar the same in Brazilian and European Portuguese?

Yes

The word "regar" is identical in meaning, spelling, and grammar in both Brazilian and Continental Portuguese. The only differences are in pronunciation, specifically regarding vowel openness, the reduction of unstressed vowels, and the rhythm of the sentence.

Brazilian Portuguese Examples

1. Você precisa regar as plantas todos os dias. (You need to water the plants every day.)
2. Eu vou regar o jardim agora à tarde. (I am going to water the garden now in the afternoon.)
3. O jardineiro está regando o gramado. (The gardener is watering the lawn.)
4. Não esqueça de regar o vaso de flores. (Don't forget to water the flower pot.)
5. É bom regar a horta depois que o sol baixar. (It is good to water the vegetable garden after the sun goes down.)

Continental Portuguese Examples

1. Tu precisas de regar as plantas todos os dias. (You need to water the plants every day.)
2. Vou regar o jardim agora à tarde. (I am going to water the garden now in the afternoon.)
3. O jardineiro está a regar o relvado. (The gardener is watering the lawn.)
4. Não te esqueças de regar o vaso de flores. (Don't forget to water the flower pot.)
5. É bom regar a horta depois que o sol baixar. (It is good to water the vegetable garden after the sun goes down.)